1. Field
Embodiments relate to a light emitting device.
2. Background
Group III-V nitride semiconductors such as GaN possess superior physical and chemical properties and, as such, are considered as important materials for semiconductor optical devices such as light emitting diodes (LED), laser diodes (LD), solar batteries, or the like.
Since optical devices employing the Group III-V nitride semiconductors emit light in blue and green bands, and have high luminance and high reliability, the optical devices are considered as a constituent material of a light emitting device.
The luminous efficacy of a light emitting device is determined by internal quantum efficiency and light extraction efficiency (also known as external quantum efficiency).
Since a nitride semiconductor layer constituting the light emitting device has a large refractive index, compared to external atmosphere, a sealing material or a substrate, the critical angle determining the range of an incidence angle of light emitted may become smaller. Thus, a large portion of light generated in an active layer is totally reflected to inner surfaces of a nitride semiconductor layer and thereby, optical loss may occur and light extraction efficiency may reduce.